Hydrogen-Enhanced Vacancy Diffusion in Metals
Name
acs.jpclett.0c01798.pdf
Description
Published version
Size
2.39 MB
Format
Adobe PDF
Checksum (MD5)
60b2392cb12373b6cc250560dfc0f835
Author(s)
Du, Jun-Ping
Geng, WT
Arakawa, Kazuto
Li, Ju
Ogata, Shigenobu
Date Issued
2020
Journal
Journal of Physical Chemistry Letters
Publisher
American Chemical Society (ACS)
Version
Final published version
Abstract
Copyright © 2020 American Chemical Society. Vacancy diffusion is fundamental to materials science. Hydrogen atoms bind strongly to vacancies and are often believed to retard vacancy diffusion. Here, we use a potential-of-mean-force method to study the diffusion of vacancies in Cu and Pd. We find H atoms, instead of dragging, enhance the diffusivity of vacancies due to a positive hydrogen Gibbs excess at the saddle-point: that is, the migration saddle attracts more H than the vacancy ground state, characterized by an activation excess ΓHm ≈ 1 H, together with also-positive migration activation volume ωm and activation entropy Sm. Thus, according to the Gibbs adsorption isotherm generalized to the activation path, a higher μH significantly lowers the migration free-energy barrier. This is verified by ab initio grand canonical Monte Carlo simulations and direct molecular dynamics simulations. This trend is believed to be generic for migrating dislocations, grain boundaries, and so on that also have a higher capacity for attracting H atoms due to a positive activation volume at the migration saddles.
MIT Department
Massachusetts Institute of Technology. Department of Nuclear Science and Engineering
Massachusetts Institute of Technology. Department of Materials Science and Engineering
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DOI of Published Version
https://doi.org/10.1021/ACS.JPCLETT.0C01798
